Check if number is a valid UK mobile number.

validate-uk-mobile-number.php

<?php
    /**
     * Function to validate if the phone number is Uk Mobile number
     * Optinal first part: '+44' or '44', also a
     * Optinal second part: '0'
     * Mandatory: 7 followed by [1-9] excluding 0,2 followed by 8 digits
     * Reference: https://en.wikipedia.org/wiki/Telephone_numbers_in_the_United_Kingdom
     *
     * @param $number
     * @return bool
     */
    function isMobileNumber($number)
    {
        return preg_match('/^(^\+(44)|(44))?(0)?(7[1|3-9][0-9]{8})$/', $number);
    }